This section provides background information related to the present disclosure which is not necessarily prior art. Gas chromatography (GC) is a common chemical analysis tool used to separate and identify target analytes, such as volatile organic compounds or semi-volatile organic compounds. GC is particularly useful for analyzing complex samples having multiple target analytes that need to be individually detected. Thus, GC is employed for analysis in a variety of different fields, including organic chemistry research; the petrochemical industry; for pharmaceutical and medical research and development; in medical and health care industries, nutrition and cosmetics, including for food, drink, flavoring, and fragrances; environmental science; and forensic sciences, among others. GC devices typically have an injector, a column, and a detector. Different chemicals or target analytes are introduced into the column in a sample via the injector and then pass through the column at different rates (due to each chemical's physical and chemical interactions with the material contained in the column). As the target analytes are eluted from (exit) the column, the detector can differentiate the species eluted over time based on the rate at which the analytes pass through the column. Such analytes can be electronically identified and/or quantified during or after the detection.
Micro-gas chromatography is conducted on a miniaturized scale from traditional gas chromatography. One specific type of micro-gas chromatography is comprehensive two-dimensional (2-D) gas chromatography (“GC×GC”). Comprehensive two-dimensional gas chromatography (GC×GC) is well-suited to analysis and separation of complex mixtures of volatile and/or semi-volatile compounds. Typically in a GC×GC separation, the sample is introduced via injection into a first chromatographic column. The target analyte species elute from this first column and can be trapped or periodically sampled by a downstream modulator device. The modulator device is disposed between the first column and the second column, and serves to continuously trap, focus, and re-inject components eluted from the first column into the second column (as a continuous injector for the second column). Thus, after collecting the eluted species from the first column, typical modulators periodically inject the collected contents into a second column at a predetermined regular interval (e.g., usually at intervals ranging from 2 to 5 seconds). Such injected fractions can be separated in the second column and elute into a downstream detector, where they can be identified and/or measured.
Generally, GC×GC or comprehensive two-dimensional gas chromatography utilizes two columns of differing selectivities connected in series by the modulator device. GC×GC provides increased peak capacity, improved peak resolution, and increased compound detectability. However, while GC×GC analysis generally provides high selectivity for analytes, it can require large amounts of energy. For example, a thermal modulator device consumes significant power during operation in a GC×GC system due to its frequent on/off cycles. Thus, improved, energy efficient gas chromatography devices and methods having high analyte selectivity and reduced processing times are needed.